To change or not to change the auto transmission fluid

[Guillaume North]

Hi all,

I've a 2006 XC70 D5 (TF80-SC 6-speed geartronic) with 107k miles. Hasn't ever toe'd and well looked after apart from never having the transmission fluid changed as far as I can tell. It changes gear fine but I'm nervous because of the stories I've heard about new fluid causing problems. I was only planning to do a simple drain and fill as it reads like this is less risky than a full flush. What do people think - is it worth it?

Thanks

[AndyV7o]

Do a progressive change to avoid problems and ease the box back to health.

The established, tried & tested procedure is as follows;
Dump sump contents, measure, refill with same amount.
Drive 200-300 miles.
Repeat step one.
Drive 500-600 miles.
Repeat step one.
Drive 1000-1200 miles.
Repeat step one.
Now you have progressively renewed the fluid fully without causing potential transmission problems by changing it all at once, and dont have half old/half new mixed fluid.
You need to do it this way because the clutches in the box become hardened, and rely on particles of friction material in the oil to help grip. If you change it all at once or do the sump dumps too soon, you wont have enough particles to help grip, the clutches slip, as they slip they get burnished and slip more, then the 'box needs a rebuild.
If you don't change it, the oil becomes sticky and there are too many particles, the combination of which means gears struggle to change, bang, lurch, etc.

Hope that is of use.
After you have managed a full progressive change, do a basic sump dump every 40k.

[Guillaume North]

That's great information - thanks

[Guillaume North]

Step 1 of above procedure plus 5.5 mile test drive complete and no issues.

Only comment to make is it took up to 300ml more to fill than what was removed. Theres a greasy patch around the transmission sump so I suspect a slow leak over the course of some years is the cause of the difference. Definitely glad to have caught this and I'm quite happy that regular drain and fills will keep on top of it going forward.

[AndyV7o]

Originally Posted by Guillaume North

Step 1 of above procedure plus 5.5 mile test drive complete and no issues.

Only comment to make is it took up to 300ml more to fill than what was removed. Theres a greasy patch around the transmission sump so I suspect a slow leak over the course of some years is the cause of the difference. Definitely glad to have caught this and I'm quite happy that regular drain and fills will keep on top of it going forward.

The fluid level should be checked when hot, you might have overfilled unless you have checked hot?

[V7025T]

Originally Posted by AndyV7o

The fluid level should be checked when hot, you might have overfilled unless you have checked hot?

...and engine running.

[Georgeandkira]

...and engine running.


....and after moving the gear range selector(stick) from P to L and back to P stopping one second in each detent.

....then checking the level promptly (20 seconds after returning to P).

[Guillaume North]

Thanks everyone for these valid comments.

Thankfully I heard about these points before starting the job and went for a short drive to warm the fluid up before draining the fill plug - I read it wants to be about 40-50oC.

Before setting off I moved through R, N, D a few times to help the box build up pressure. Got this point from a good youtube vid - https://www.youtube.com/watch?v=a5h4UhUSHS4&t=11s

Also removed the level plug with car running in park on the flat.

First time I followed this procedure only a few drops of fluid came out the level plug. Went back and put another 400ml in (bearing in mind I also put an extra 200ml or so in the first time). Second time I undid the level plug about 200ml came out.